Old English meter is a richly enigmatic research topic. There is a usual form, with four metrical positions per verse supporting a range of accentual contours, which are schematized as five "types" (G Typen) in the influential theory of Eduard Sievers. Then there are eccentricities whose raison d'être has not been adequately explained. Chief among these is so-called hypermetric verse (G Schwellvers), verses of five positions or more that tend to cluster in passages of enhanced drama or sententiousness. Instead of locating hypermetric verses in the hinterlands of normal Old English meter, Megan E. Hartman focuses directly on their form and style, with comparisons to analogous extended meters in Old Norse and Old Saxon poetry. The result is a reorientation of prosodic perspective, like visiting Brobdingnag after long residence in Lilliput.
Each chapter follows the same itinerary. First comes metrical structure, then the interface between meter and syntax, then rhetoric and style. Chapters 1, 2, and 5 analyze hypermetric verses in, respectively, three categories of Old English poems. These are "conservative" poetry (Beowulf, Daniel, Exodus, Genesis A, and Guthlac A), establishing a baseline; "gnomic" poetry (Fortunes of Men, Maxims I and II, Order of the World, Precepts, Rune Poem, and Solomon and Saturn II), departures from the norm; and "late" poetry (Judith, with comparisons to normal meter in Battle of Brunanburh, Battle of Maldon, Death of Edgar, Death of Edward, and Judgment Day II), a reinstatement of the norm with a difference. Chapters 3 and 4 discuss Old Norse and Old Saxon extended meters. The analogy between these and Old English hypermetric verse is inexact (pp. 90, 126). Norse poets had three meters at their disposal, two of which, ljóðaháttr and málaháttr, are "hyper-" in relation to the third, fornyrðislag. Poets can indulge in "metrical shifting" (121). Old Norse poems discussed are Átlamál, Eiríksmál, Fáfnismál, Hákonarmál, Haraldskæði, Hávamál,Sigdrífumál, and Skírnismál. Hartman finds that ljóðaháttr and málaháttr "separately fulfill the major [stylistic] functions of hypermetric composition in Old English" (99). Old Saxon has hypermetric verse, but it is less sharply distinguished from normal verse, due to metrical and linguistic differences, and so in chapter 4 Hartman weighs the stylistic implications of formal ambiguity. She describes hypermetric verse as a tool; an archaeologist of prosody, she asks what the tool was for. The book features a number of effective close stylistic expositions of individual passages. Key texts include Daniel, whose "fluid style" (25) marks it out from the other Old English narrative poems; Maxims I, an eccentric among eccentrics; the Heliand, the Old Saxon religious epic whose hypermetric play contributes to its evangelical purpose; and Judith, a poem that turns traditional forms of hypermetric verse to an unwonted "solemnity" (181). Throughout, Hartman conveys the overdetermination of the choice to switch into hypermetric meter. "[A] single hypermetric passage can perform multiple [stylistic] functions at once" (196).
Poetic Style and Innovation in Old English, Old Norse, and Old Saxon succeeds as a refinement of metrical description. Hartman's theory of hypermetric verse structure, elaborated in articles precipitating this book and summarized in the introduction (9), is superior to published opinions of prior researchers--although Nicolay Yakovlev's unpublished 2008 DPhil thesis (not cited by Hartman) anticipates certain of her conclusions.  Hartman analyzes the hypermetric verse into an "onset" of one or more positions followed by a four-position "cadence" that coincides with a normal verse pattern. Onsets are either "strong," beginning with a metrically stressed syllable, or "weak," a string of two or more metrically unstressed syllables. These distinctions are pivotal for Hartman, enabling comparisons of metrical style across and within poems. The hypermetric alliterative long line is internally differentiated by onset. Generally, the "on-verse" or first half of the line takes a strong onset and the "off-verse" or second half of the line takes a weak onset. Some poets do mix and match. Hartman attends closely to both structure and distribution of hypermetric verses. To appreciate her analysis and notation one must already be conversant with the Sieversian metrical tradition. Studies by R. D. Fulk, Geoffrey Russom, and Seiichi Suzuki are frequently cited. Readers lacking this background will struggle to follow the exposition in the first half of each chapter. This is not a book for beginners. For example, Hartman nowhere defines or defends such a fundamental point as the theory of "four positions" (90) that constitute a normal verse or the cadence of a hypermetric verse. Terms of art in Sieversian notation, such as drop, foot, and Type D*, irrupt into Hartman's prose without warning or explication. That notation is confusing when applied to Old Norse poetry (91 n. 2), which, according to Hartman's own scansions, has different metrical templates and different rules for mapping language onto meter.
While thus half-concealed from the unsuspecting reader, the procedures of Germanic philology catalyze new insights. The argument of chapter 2, that poetic formulae torque meter in the gnomic poems, is convincing. It reminds of Gregory Nagy's arguments about Homeric formulae.  Hartman is especially good on the linguistic and stylistic factors affecting verb placement. In the tradition of Chomskyan syntax, she parses the alliterative long line into nested binary pairs of more and less subordinated positions and assesses syntax in relation to that (never-stated) architecture. As in the work of Daniel Donoghue, Calvin B. Kendall, and Haruko Momma, a critical perspective at the intersection of meter and syntax illuminates the interdependence of the two domains in poetic practice. Hartman finds that poets compensate for metrical complexity by mitigating syntactic complexity. This tradeoff lends hypermetric passages a paradoxically heightened and relaxed feel, a difference from normal composition that poets exploit variously in "each hypermetric moment" (37). If Hartman's scansion betrays an inconsistent treatment of finite verbs, which have variable metrical value according to context, that is a problem she inherits from the Sieversian system, one criticized by Thomas Cable and Russom among others (29 n. 17, citing Russom). She does not attempt to solve the problem herself or to adopt Cable's or Russom's preferred solution; emphasis falls on tabulation of metrical difference as opposed to theorization as such.
On the literary side, Hartman overstates the novelty of her approach to "the literary implications of Germanic meter" (1). Her bibliography, including stylistically attuned studies by Mary Blockley, Cable, Constance B. Hieatt, and Momma, shows this topic to be already at an advanced state of study. Where metrical style shades into poetics, Hartman's bibliography has gaps. Nevertheless, her focus on hypermetric verse articulates a new sense of the contours of the poetic corpus and a "wider range of hypermetric effects" (126) than anyone had noticed before. The book is least compelling when Hartman rehearses tenets of nineteenth-century medievalism, such as the idea of an "immanent tradition" (74) of gnomic poetry or a unified "Germanic ideology" (44), "Germanic heroic tradition" (150), or "Germanic literature" (151). Chapters 3 and 4 in fact locate Old English in an expanded field of metrical variety, not more of the same. She is most convincing when expounding the stylistic sophistication of otherwise-minor poems like Haraldskvæði and Judith. One readymade metric for literary style is furnished by Hans Kuhn's so-called laws of metrical syntax, which dictate the placement of metrically unstressed words in the clause. Hartman repeatedly associates conformity to Kuhn's laws with a "high style" (140), an association that is plausible but remains unhistoricized here. Hartman appears disinclined to historicize questions of form. A paragraph in the introduction (1-2) discusses the relation of genre and meter in the sixteenth century, and the clear implication there is that one can impute the same understanding of metrical decorum to much earlier authors. In general, Hartman's findings flag up literary-historical conclusions she herself does not reach, such as the mutual influence, if any, between the gnomic poems and the Seafarer and the Wanderer, or the reasons behind the gradual abandonment of hypermetric composition in the tenth and eleventh centuries, or the possibility of metrical diplomacy between Old English and Old Saxon literatures beyond Genesis B.
There are other distancing gestures. In preambles, asides, and footnotes, Hartman brackets questions of metrical change, dating, genre, and textual criticism. That is understandable. Metrical description has quite enough complexity of its own. And yet those questions everywhere intersect metrical and stylistic analysis, disrupting the conclusions one would have wished to draw from an ideal corpus. Assumptions about metrical history, chronology, literary ecology, and editing are tucked away in footnotes. Thus Hartman's "conservative" poems are conservative because Fulk and Russom say they are (15 nn. 1-2); the "gnomic poems" belong together because they were collated by T. A. Shippey (54 n. 4); Old English meter before Judith was "stable" (162) because that is how Fulk and Russom frame it (no footnote); certain possibly hypermetric verses are thrown out because editors have doubted whether they transmit authorial readings (8-9 n. 7). Because she registers the controversies surrounding these topics obliquely, readers not in the know will miss the extent to which Hartman's judgments (like any judgments) are partial. I am not necessarily disagreeing with them. The book makes a strong case for the validity of grouping Old English poems into "conservative," "gnomic," and "late" according to hypermetrical usage. One wonders whether these labels hold for normal verse, and whether the implied claims about chronology and genre are true. To relabel the three groups, say, "historicizing," "expository," and "contemporizing," would imply totally different claims about early English literary culture without altering the metrical bases of the distinctions themselves.
Overall, Hartman's scansions, statistics, and translations are reliable. I noticed a few mistranslations, of which the most consequential was "earm se him his frynd geswicað" (Maxims I 37b) twice translated "wretched is he who deceives his friends" (73, 86), when it means the opposite, "wretched is he whose friends deceive him." I could not see why table 3.1 was oriented orthogonally to the other finite-verb tables, 1.2, 2.2, 4.1, and 5.4.
Poetic Style and Innovation renders Old English poems that use hypermetric verse more visible, and more clearly crafted as literary texts, than ever before. Comparisons to Old Norse and Old Saxon add linguistic and geographical depth. Old English emerges at a unique conjunction of metrical singularity and metrical diversity. The next step for the research program begun here is to bring the analysis to bear on the difficulties of historical evidence, survival, and change that dog the study of early poetries.
1. Nicolay Yakovlev, "The Development of Alliterative Metre from Old to Middle English" (diss., University of Oxford, 2008), pp. 83–88. In different words, Yakovlev anticipates Hartman's distinction between onset and cadence. Yakovlev provides an account compatible with Hartman's but narrower and stricter, insofar as he excludes from consideration the gnomic poems whose hypermetric style is more eclectic. Hartman's scansions could have benefited from Yakovlev's observation that the cadence must not have a long dip (sequence of two or more metrically unstressed syllables), which mirrors restrictions on dips in normal meter and thus supports Hartman's conclusion that "many of the metrico-syntactic features that govern normal verse are maintained in hypermetric composition" (16). To perceive the restriction on dips in both varieties of Old English meter one must acknowledge the variable metrical value of verbal prefixes and the negative particle ne, a nuance that Hartman has not absorbed. Prefixes and ne may be either counted as unstressed or omitted from the metrical count altogether, as context demands.See Yakovlev, "Development of Alliterative Metre," 57–60, and Ian Cornelius, Reconstructing Alliterative Verse: The Pursuit of a Medieval Meter (Cambridge: Cambridge University Press, 2017), 56–57 and 89–90.
2. Gregory Nagy, Comparative Studies in Greek and Indic Meter (Cambridge, MA: Harvard University Press, 1974).